Polyisocyanurate foam

ABSTRACT

Polyisocyanurate foam in which the polyol content is largely a polyol mixture prepared by the transesterification with a glycol of a residue obtained from the manufacture of dimethyl terephthalate and in which the foam has been prepared using fluorocarbon blowing agent and amine triol to improve compatibility between the polyol and the blowing agent.

BACKGROUND OF THE INVENTION

U.S. Pat. No. 4,237,238 describes improved polyisocyanurate foamobtained by bringing together in the presence of a blowing agent andtrimerization catalyst an organic polyisocyanate and a polyol mixtureprepared by the transesterification, with a glycol of molecular weightfrom about 60 to about 400, of a residue obtained from the manufactureof dimethyl terephthalate. Polyol mixtures of this type are described ingreater detail in U.S. Pat. No. 3,647,759 and are available commerciallyfrom Hercules, Inc., Wilmington, Del. under the tradename Terate®Resins.

The foams described in U.S. Pat. No. 4,237,238 are said to becharacterized by a high degree of fire resistance with low smokeevolution on combustion and low foam friability. Unfortunately, polyolsof the type described in the U.S. Pat. No. 4,237,238 patent have poorcompatibility with the fluorocarbon blowing agents, especiallymonofluorotrichloromethane, which are generally preferred in theindustry for use in making rigid polyurethane and polyisocyanuratefoams. To deal successfully with this poor compatibility it hasfrequently been necessary to introduce the blowing agent by separatestream (which is relatively inefficient since it allows blowing agent toat least partially separate prior to foaming) or to mix polyols of thetype described above with other polyols to improve the overallcompatibility of the polyol mixture with the blowing agent. It has alsobeen indicated in the literature that methoxylated nonylphenylsurfactant is effective in improving compatibility between fluorocarbonblowing agents and polyols of the type described above (journal ofcellular plastics May/June 1980 page 52-158). There is, however, a needfor more effective improvement in compatibility that is afforded by suchnonylphenyl surfactants.

U.S. Pat. No. 4,339,343 discloses miscible blends of 20-85% alkoxylatedalkyl amines with 15-80% primary hydroxyl polyols and fluorocarbonblowing agent, but does not contemplate the use of the special type ofpolyols described in U.S. Pat. Nos. 4,237,238 and 3,647,759.

SUMMARY OF THE INVENTION

In accordance with the present invention it has now been found thatcompatibility of fluorocarbon blowing agents with the type of polyolsdescribed in U.S. Pat. Nos. 4,339,238 and 3,647,759 is substantiallyimproved by use of small amounts of amine triol of the general typedisclosed in U.S. Pat. No. 4,289,858. By using amine triol as describedherein, compatibility between the polyols and fluorocarbon blowingagents is sufficiently improved so that normal production techniques maybe employed in manufacturing rigid polyisocyanurate foam where betweenabout 60% and 100 wt % of the polyol is of the type described above.This allows full advantage to be taken of the tendency of this type ofpolyol to produce rigid foams of low friability, K factor, flammabilityand cost.

The invention includes rigid cellular polyisocyanurate foam and reactionmixture suitable for making rigid foam. The rigid foam of the inventioncomprises the post cured reaction product of reacting aromaticpolyisocyanate with between about 0.1 and about 0.5 hydroxyl equivalentof polyol per equivalent of said polyisocyanate, said polyol comprisingat least about 60 percent of a polyol mixture prepared by thetransesterification with a glycol of molecular weight from about 60 toabout 400 of a residue remaining after dimethyl terephthalate and methylp-toluate have been removed from a dimethyl terephthalate esterifiedoxidate reaction product, the major portion of said residue comprising amixture of methyl and benzyl esters of benzene and biphenyl di- andtricarboxylic acids. The reaction of polyisocyanate and polyol takesplace in the presence of:

(a) isocyanate trimerization catalyst;

(b) fluorocarbon blowing agent; and

(c) between about 0.1 and about 15 wt % based on total polyol of aminetriol of the formula ##STR1## wherein R₁ is an alkyl group containingfrom 8 to about 30 carbon atoms, each R₂ is independently H or CH₃, n is2 or 3 and x+y+z is an integer from 3 to about 50.

Reaction mixture of the invention comprises:

(a) fluorocarbon blowing agent;

(b) isocyanate trimerization catalyst;

(b) polyol comprising at least about 60 percent polyol mixture preparedby the transesterification with a glycol of molecular weight from about60 to about 400 of residue remaining after dimethyl terephthalate andmethyl p-toluate have been removed from dimethyl terephthalateesterified oxidate reaction product, the major portion of said residuecomprising a mixture of methyl and benzyl esters of benzene and biphenyldi- and tricarboxylic acids; and

(d) between about 0.1 and about 15 wt % based on total polyol of aminetriol of the formula ##STR2## wherein R₁ is an alkyl group containingfrom 8 to about 30 carbon atoms, each R₂ is independently H or CH₃, n is2 or 3 and x+y+z is an integer from 3 to about 50.

DETAILED DESCRIPTION OF THE INVENTION

Amine triols used in the present invention have the general formula##STR3## wherein R₁ represents an alkyl group containing from 8 to about30 carbon atoms, each R₂ is independently H or CH₃, n is 2 or 3 andx+y+z is an integer from 3 to about 50. Amine triols of this type ormixtures thereof in which R₁ represents an alkyl group containingbetween about 12 and about 20 carbon atoms and in which x+y+z equals aninteger between 3 and about 10 are preferred. Amine triols are used inthe invention in amounts of between about 0.1 and about 15 weightpercent (wt %), preferably between about 1 and about 6 wt %, based ontotal polyol used. Since the amine triols used in the invention arethemselves polyols they must be considered in determining the totalpolyol content of the reaction mixture or rigid foam of the invention.

Amine triols of the general type used in the invention and theirpreparation are described in detail in U.S. Pat. No. 4,289,858 thedisclosure of which is incorporated herein by reference. Where n=2, suchamine triols can for instance be prepared by reacting the appropriateprimary amine or mixture of amines with ethylene oxide or propyleneoxide. The resulting aminoalcohol can then be transformed into thediamine, as by reacting with ammonia, followed by reaction with about3-30 molar proportions of ethylene oxide or propylene oxide or mixturesthereof to form the desired amine triol. Where n=3, the amine triol maybe prepared by cyanoethylating the primary amine starting material withappropriately substituted acrylonitrile and reducing to form diaminewhich may then be alkoxylated with from about 3 to about 15 molarproportions of ethylene oxide or propylene oxide or mixtures thereof toform the desired amine triol. Suitable amine starting materials includefor instance oleyl amine, stearyl amine, octylamine, dodecylamine,hexadecylamine, decenylamine, tetradecenylamine, octadecenylamine andmixtures thereof such as cocoamine (typically a mixture of about 2 wt%decylamine, 53 wt% dodecylamine, 24 wt% tetradecylamine, 11 wt%hexadecylamine, 5 wt% octadecylamine, and 5 wt% octadecenylamine); soyaamine (typically a mixture of about 11.5 wt% hexadecylamine, 4 wt%octadecylamine, 24.5 wt% oleylamine, 53 wt% linoleylamine, and 7 wt%linolenylamine); tallow amine (typically a mixture of about 4 wt%tetradecylamine, 29 wt% hexadecylamine, 20 wt% octadecylamine, and 47wt% octadecenylamine). Further illustrative of suitable starting aminesare the halogenated amines, particularly the chlorinated and brominatedfatty amines, which, illustratively, can be made by the chlorination orbromination of cocoamine, soya amine, tallow amine, and the like. Tallowamine mixtures are especially preferred.

As mentioned polyol is used in foams of the invention in amounts betweenabout 0.1 and about 0.5 hydroxyl equivalent of total polyol perequivalent of polyisocyanate. Use of between about 0.15 and about 0.25hydroxyl equivalent of polyol on the same basis is frequently preferred.Polyol used in forming reaction mixture and foam of the inventioncomprises at least about 60 wt%, preferably at least about 75 wt%, andstill more preferably at least about 95 wt% of polyol mixture preparedby transesterification with a glycol of molecular weight from about 60to about 400 of a residue remaining after dimethyl terephthalate andmethyl p-toluate have been removed from a dimethyl terephthalateesterified oxidate reaction product, the major portion of said residuecomprising a mixture of methyl and benzyl esters of benzene and biphenyldi- and tricarboxylic acids. Such polyol mixtures are described indetail in U.S. Pat. No. 4,237,238 the disclosure of which isincorporated herein by reference.

The transesterified polyol mixture may be prepared by heating theresidue defined above with the transesterifying glycol in accordancewith the procedures described in U.S. Pat. No. 3,647,759 the disclosureof which is also incorporated herein by reference.

The transesterifying step is simply the replacement of the non-hydroxylcontaining carbomethoxy groups in the various aromatic esters of theresidue by the glycol agents so that the ester groups now contain, forthe most part, terminal hydroxyl groups. Illustrative of the esterifyingglycols which can be employed are ethylene glycol, 1,3-propylene glycol,1,2-propylene glycol, 1,4-butanediol, 1,2-hexanediol, 1,6-hexanediol,diethylene glycol, dipropylene glycol, tripropylene glycol,polyoxyethylene glycols, and polypropylene glycols. A preferred group ofglycols consists of ethylene glycol and diethylene glycol with thelatter being most peferred.

Examples of ethylene glycol and diethylene glycol transesterifiedresidues which are used in accordance with the present invention arethose produced commercially under the tradename of Terate® resins andsupplied by Hercules Inc., Wilmington, Del. Polyol viscosity sometimesrequires adjustment or modification in order to balance componentpumping ratios or to satisfy some other processing requirement. Althoughthe polyol mixtures can be readily produced as fluid materials,particularly by employing excess glycol transesterifying agent andleaving residual glycol in the resin, it is also feasible to employadditional diluents with the polyol mixtures.

As mentioned the polyol mixtures described above must comprise at leastabout 60 wt % and preferably at least about 75 wt % of the total polyolcontent of reaction mixtures and foams of the invention. The remainingpolyol content, if any, of reaction mixtures and foams of the inventionmay be any polyol of the type conventionally used in making rigidpolyurethane and polyisocyanurate foams. Suitable polyols include forinstance those mentioned in U.S. Pat. No. 4,094,869 the disclosure ofwhich is incorporated herein by reference.

Polyisocyanate suitable for use in forming foams of the invention may beany of the conventional aromatic polyisocyanates known for use in themanufacture of polyuethane foams or may be mixtures of suchpolyisocyanates. Suitable polyisocyanates generally have at least twoisocyanate groups per molecule and include, for instance, the aromaticpolyisocyanates described in more detail in U.S. Pat. No. 4,094,869, thedisclosure of which is incorporated herein by reference. Preferredpolyisocyanates are methylene bridged isocyanates of the type describedin U.S. Pat. No. 4,094,869. These preferred polymethylene polyphenylpolyisocyanates are characterized by the general formula: ##STR4##wherein n is predominantly an integer of 1 or 0 or a mixture wherein nis primarily 1 in a preferred embodiment and to a lesser extent 0, andthus the trimer, dimer or mixtures thereof, and where as preferred, thisisocyanate is used in an undistilled state, will include residual ortrace amounts of high polymers as well. The average isocyanatefunctionality of these polymers is consequently in the range of about2.25 to about 3.2 or higher. The polyphenyl polymethylenepolyisocyanates thus employed are available commercially, for example,under the tradenames Mondur MR, PAPI and AFPI. They are liquid and havea reduced viscosity of about 50-500 centipoises at 25° centigrade (C.).

Preferred polyisocyanates as described herein may be obtained byphosgenation of mixtures of the corresponding methylene-bridgedpolyphenyl polyamines. The latter are secured by the hydrochloric-acidcatalyzed condensation of primary aromatic amines such, illustratively,as aniline, using procedures well known in the art.

The isocyanate trimerization catalyst employed in the invention can beany catalyst known to those skilled in the art which will catalyze thetrimerization of an organic isocyanate compound to form the isocyanuratemoiety. Trimerization catalyst is usually used in amounts between about0.1 and about 5 wt% based on polyisocyanate. Most commonly usedtrimerization catalysts also function to catalyze the reaction of polyoland isocyanate to form urethane. The use of such dual function catalystsis preferred, but a separate catalyst may if desired be used forurethane formation. If used, urethane catalyst is normally used inamounts between about 0.05 and 3 wt% based on polyisocyanate. Suitabledual function catalysts include for instance one or more metalcarboxylates such as potassium acetate, potassium octoate, sodiumoctoate or calcium octoate. Mixtures of such carboxylates with tertiaryamines are also suitable as are N-hydroxyl-alkyl quaternary ammoniumcarboxylates. Suitable urethane catalysts include for instance tertiaryamines such as triethyl amine or dimethyl ethanol amine as well as1,4-diaza dicyclo-octane (2,2,2) and organo tin compounds such asdibutyltin diacetate, stannous octoate and dibutyltin dilaurate.

Fluorocarbon blowing agent is normally used in amounts between about 5and about 50 wt%, preferably between about 10 and about 35 wt% based onpolyisocyanate with the amount used depending largely upon the desiredfoam density. The amount used will affect foam density and closed cellcontent of the foam. This will usually result in blowing agent beingpresent in reaction mixture of the invention in amounts between about 15and about 175 wt% based on total polyol. Trichlorofluoromethane ispreferred. Other suitable blowing agents include for instancedichlorodifluoromethane, 1,1-dichloro-1-fluoroethane,hexafluorocyclobutene and octafluorocyclobutane.

Foaming agents and other optional additives such as dispersing agents,cell stabilizers, surfactants, flame retardants, and the like, can beemployed according to the teachings of the patents referred to above.Use of flame retardants tends to even further improve compatibility ofthe polyols and blowing agents used in accordance with the invention. Inthis respect tris(dichloropropylphosphate) is a preferred flameretardant for use in the invention.

A conventional surfactant such as a silicone surfactant is preferablyincorporated in the reaction system of the invention in amounts betweenabout 0.5 and about 3 wt% based on isocyanate in order to stabilize, inconjection with the catalyst present, the cellular foam product.Illustrative of these are the polyoxalkylenepolydimethyl-siloxane blockcopolymers. Other nonionic, cationic, and anionic surface active agentsmay also be used.

The proportion of isocyanate groups to hydroxyl groups in the reactantpolyols described above (and thus including the unhalogenated,halogenated and, where present, nitrogen-containing, polyols) isdesirably from 2 to 10, and preferably 4 to 7, to 1, respectively. Thusthe polyisocyanates are employed in amounts that provide from 200 to1000, and preferably 400 to 700, percent of the stoichiometric amount ofthe isocyanate groups required to react with all of the hydroxyl groupspresent in the reactant polyols. Expressed in an alternative manner,reaction mixture and rigid foams of the invention comprise between about0.1 and about 0.5 and preferably between about 0.15 and about 0.25hydroxyl equivalent of polyol per equivalent of polyisocyanate. Howeverexpressed, it is critical to the invention that more than fifty percentof the isocyanate groups of the polyisocyanate reactant be free to reactand form triazanone moieties within the foam structure.

Reaction mixture of the invention may be formed by mixing the requiredingredients of the foam (except for the polyisocyanate) in any suitablemanner such as by introducing all of the ingredients into a suitablecontainer or receptical and stirring or blending to obtain a relativelystable, homogeneous mixture. The ingredients may be introducedsequentially or simultaneously. Polyisocyanate is then added to initiatethe reactions necessary to make rigid foams of the invention. Reactionmixture of the invention may for instance be combined withpolyisocyanate immediately prior to or simultaneously with thedispensing of the mixture onto a moving conveyor belt to foam themixture to form rigid foam which may be post cured, all in aconventional manner. Post curing is generally carried out in the absenceof moisture at ambient or, if desired to accelerate the cure, atelevated temperatures, the permissible range being desirably about 20°C. to 90° C. for periods of time which will vary inversely with thecuring temperature employed and varying from about 1 to about 48 hours.This post cure serves to complete the formation substantially of trimerwithin the foam structure.

Because of the improved compatibility between ingredients due to thepresence of the amine triols, reaction mixture of the invention hasgreatly improved stability. Depending upon such factors as storagetemperature, amount of agitation during storage, presence of surfactantor flame retardant and amounts and type of polyols and amine triol used,reaction mixtures of the invention will remain homogeneous with nonoticeable separation of blowing agent for periods of time ranging froma few minutes to almost indefinitely. In many instances reaction mixtureof the invention will remain stable and homogeneous for at least about10 minutes. This allows the mixtures to be completely formed and thenstored for at least a short time before use. By contrast, in reactionmixtures of this general type taught by the prior art, e.g. U.S. Pat.No. 4,237,238, the fluorocarbon blowing agent begins to separate almostimmediately so that uneven foam results if the mixture is not usedimmediately.

The following example is intended to illustrate the invention withoutlimiting the scope thereof.

EXAMPLE

Rigid foam of the invention may be made in a conventional manner fromreaction mixture of the invention comprising the following ingredients:

    ______________________________________                                        Ingredient             Parts by Weight                                        ______________________________________                                        Terate ® 203 polyol                                                                              100                                                    Trichlorofluoromethane 92.5                                                   blowing agent                                                                 Tris(dichlororpropylphosphate)                                                                       35.5                                                   flame retardant                                                               N(hydroxyalkyl)        5.0                                                    quaternary ammonium                                                           carboxylate catalyst                                                          Silicone surfactant    5.8                                                    (Dow Croning DC-193)                                                          Amine diol compatibility                                                                             2.5                                                    agent having the structure                                                     ##STR5##                                                                     ______________________________________                                    

wherein R₁ is a mixture of alkyl groups averaging about 18 carbon atoms,n is 2 and x+y+z=5. Terate® 203 polyol is supplied by Hercules, Inc.,and consists entirely of polyol mixture prepared by thetransesterification with a glycol of molecular weight from about 60 toabout 400 of a residue remaining after dimethyl terephthalate and methylp-toluate have been removed from a dimethyl terephthalate esterifiedoxidate reaction product, the major portion of said residue comprising amixture of methyl and benzyl esters of benzene and biphenyl di- andtricarboxylic acids.

To the above reaction mixture may be added 332 parts by weight ofpolymethylene polyphenyl polyisocyanate having an isocyanate equivalentof 425 (obtainable from Mobay Chemical Company under the tradenameMondur® MR). The resulting mixture may then be immediately heated anddispensed onto a moving conveyor belt to produce rigid foam in aconventional manner.

While the invention has been described above with respect to preferredembodiments thereof, it will be understood by those skilled the art thatvarious changes and modifications may be made without departing from thespirit or scope of the invention.

What is claimed is:
 1. Rigid cellular polyisocyanurate foam comprisingthe post cured reaction product of reacting aromatic polyisocyanate withbetween about 0.1 and about 0.5 hydroxyl equivalent of polyol perequivalent of said polyisocyanate, said polyol comprising at least about60 percent polyol mixture prepared by the transesterification with aglycol of molecular weight from about 60 to about 400 of a residueremaining after dimethyl terephthalate and methyl p-toluate have beenremoved from a dimethyl terephthalate esterified oxidate reactionproduct, the major portion of said residue comprising a mixture ofmethyl and benzyl esters of benzene and biphenyl di- and tricarboxylicacids, said reaction of polyisocyanate and polyol taking place in thepresence of:(a) isocyanate trimerization catalyst; (b) fluorocarbonblowing agent; and (c) between about 0.1 and about 15 wt% based on totalpolyol of amine triol of the formula ##STR6## wherein R₁ is an alkylgroup containing from 8 to about 30 carbon atoms, each R₂ isindependently H or CH₃, n is 2 or 3 and x+y+z is an integer from 3 toabout
 50. 2. Rigid foam according to claim 1 wherein, in the formula forthe amine triol, R₁ represents an alkyl group containing between about12 and about 20 carbon atoms and x+y+z equals an integer between 3 andabout
 10. 3. Rigid foam according to claim 1 wherein total polyol ispresent in amounts sufficient to supply between about 0.15 and about0.25 hydroxyl equivalent of polyol per equivalent of polyisocyanate. 4.Rigid foam according to claim 1 wherein said polyol prepared bytransesterification of residue comprises at least about 75 percent ofthe total polyol.
 5. Rigid foam according to claim 1 wherein thearomatic polyisocyanate comprises polymethylene polyphenylpolyisocyanate characterized by the general formula: ##STR7## wherein nis predominantly an integer of 1 or
 0. 6. Rigid foam according to claim1 wherein the blowing agent is trichlorofluoromethane.
 7. Rigid foamaccording to claim 1 wherein amine triol is present in an amount betweenabout 1 and about 6 wt% based on total polyol.
 8. Rigid foam accordingto claim 1 wherein said blowing agent is present in an amount betweenabout 5 and about 50 wt% based on polyisocyanate.
 9. Rigid foamaccording to claim 1 wherein said polyol prepared by transesterificationof residue comprises at least about 95 percent of the polyol in saidmixture.
 10. Rigid foam according to claim 1 wherein said blowing agentis present in an amount between about 10 and about 35 wt% based onpolyisocyanate.
 11. Rigid foam according to claim 1 wherein:(a) in theformula for the amine triol, R₁ represents an alkyl group containingbetween about 12 and about 20 carbon atoms and x+y+z equals an integerbetween 2 and about 10; (b) polyol is used in amounts sufficient tosupply between about 0.15 and about 0.25 hydroxyl equivalent of polyolper equivalent of polyisocyanate; (c) said polyol prepared bytransesterification of residue comprises at least about 95 percent ofthe total polyol; (d) the aromatic polyisocyanate comprisespolymethylene polyphenyl polyisocyanate characterized by the generalformula: ##STR8## wherein n is predominantly an integer of 1 or 0; (e)amine triol is present in an amount between about 1 and about 6 wt%based on total polyol; and (f) the blowing agent istrichlorofluoromethane and is present in an amount between about 10 andabout 35 wt% based on polyisocyanate.
 12. Reaction mixturecomprising:(a) fluorocarbon blowing agent; (b) polyol comprising atleast about 60 percent polyol mixture prepared by thetransesterification with a glycol of molecular weight from about 60 toabout 400 of residue remaining after dimethyl terephthalate and methylp-toluate have been removed foam dimethyl terephthalate esterifiedoxidate reaction product, the major portion of said residue comprising amixture of methyl and benzyl esters of benzene and biphenyl di- andtricarboxylic acids; and (c) between about 0.1 and about 15 pounds perhundred pounds total polyol of amine triol of the formula ##STR9##wherein R₁ is an alkyl group containing from 8 to about 30 carbon atoms,each R₂ is independently H or CH₃, n is 2 or 3 and x+y+z is an integerfrom 3 to about
 50. 13. Reaction mixture according to claim 12 wherein,the formula for the amine triol, R₁ represents an alkyl group containingbetween about 12 and about 20 carbon atoms and x+y+z equals an integerbetween 3 and about
 10. 14. Reaction mixture according to claim 12wherein said polyol prepared by transesterification of residue comprisesat least about 75 percent of the polyol in said mixture.
 15. Reactionmixture according to claim 12 wherein the aromatic polyisocyanatecomprises polymethylene polyphenyl polyisocyanate characterized by thegeneral formula: ##STR10## wherein n is predominantly an integer of 1 or0.
 16. Reaction mixture according to claim 12 wherein the blowing agentis trichlorofluoromethane.
 17. Reaction mixture according to claim 12wherein the amine triol is present in an amount between about 1 andabout 6 pounds of amine triol per hundred pounds of total polyol. 18.Reaction mixture according to claim 12 wherein said polyol prepared bytransesterification of residue comprises at least about 95 percent ofthe polyol in said mixture.
 19. Reaction mixture according to claim 12wherein the blowing agent is trichlorofluoromethane and is present in anamount between about 15 and about 175 wt% based on polyol.
 20. Reactionmixture according to claim 12 wherein:(a) in the formula for the aminetriol, R₁ represents an alkyl group containing between about 12 andabout 20 carbon atoms and x+y+z equals an integer between 2 and about10; (b) said polyol prepared by transesterification of residue comprisesat least about 95 percent of the polyol in said mixture; (c) the aminetriol is present in an amount between about 1 and about 6 wt% based ontotal polyol; and (d) the blowing agent is trichlorofluoromethane and ispresent in an amount between about 15 and about 175 wt% based on totalpolyol.